Data transport in a virtualized distributed antenna system

ABSTRACT

A system for routing signals in a Distributed Antenna System includes a plurality of local Digital Access Units (DAUs) located at a Local location. Each of the plurality of local DAUs is coupled to each other and operable to route signals between the plurality of local DAUs. Each of the plurality of local DAUs includes one or more Base Transceiver Station (BTS) RF connections. Each of the plurality of BTS RF connections is operable to be coupled to one of one or more sectors of a BTS. The system also includes a plurality of remote DAUs located at a Remote location. The plurality of remote DAUs are coupled to each other and operable to transport signals between the plurality of remote DAUs.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 13/754,702, filed on Jan. 30, 2013, entitled “Date Transport ina Virtualized Distributed Antenna System,”, which claims benefit under35 U.S.C. §119(e) of U.S. Provisional Patent Application No. 61/592,747,filed on Jan. 31, 2012, entitled “Data Transport in a VirtualizedDistributed Antenna System.” The disclosures of these applications arehereby incorporated by reference in their entirety for all purposes.

BACKGROUND OF THE INVENTION

Wireless communication systems employing Distributed Antenna Systems(DAS) are available. A DAS typically includes one or more host units,optical fiber cable or other suitable transport infrastructure, andmultiple remote antenna units. A radio base station is often employed atthe host unit location commonly known as a base station hotel, and theDAS provides a means for distribution of the base station's downlink anduplink signals among multiple remote antenna units. The DAS architecturewith routing of signals to and from remote antenna units can be eitherfixed or reconfigurable.

A DAS is advantageous from a signal strength and throughput perspectivebecause its remote antenna units are physically close to wirelesssubscribers. The benefits of a DAS include reducing average downlinktransmit power and reducing average uplink transmit power, as well asenhancing quality of service and data throughput.

Despite the progress made in wireless communications systems, a needexists for improved methods and systems related to wirelesscommunications.

SUMMARY OF THE INVENTION

The present invention generally relates to wireless communicationsystems employing Distributed Antenna Systems (DAS) as part of adistributed wireless network. More specifically, the present inventionrelates to a DAS utilizing a software configurable radio (SCR). In aparticular embodiment, the present invention has been applied to the useof coupled remote Digital Access Units. The methods and systemsdescribed herein are applicable to a variety of communications systemsincluding systems utilizing various communications standards.

Wireless and mobile network operators face the continuing challenge ofbuilding networks that effectively manage high data-traffic growthrates. Mobility and an increased level of multimedia content for endusers typically employs end-to-end network adaptations that support newservices and the increased demand for broadband and flat-rate Internetaccess. One of the most difficult challenges faced by network operatorsis caused by the physical movement of subscribers from one location toanother, and particularly when wireless subscribers congregate in largenumbers at one location. A notable example is a business enterprisefacility during lunchtime, when a large number of wireless subscribersvisit a lunch room or cafeteria location in the building. At that time,a large number of subscribers have moved away from their offices andusual work areas. It's likely that during lunchtime, there are manylocations throughout the facility where there are very few subscribers.If the indoor wireless network resources were properly sized during thedesign process for subscriber loading as it is during normal workinghours when subscribers are in their normal work areas, it is very likelythat the lunchtime scenario will present some unexpected challenges withregard to available wireless capacity and data throughput.

According to an embodiment of the present invention, a system forrouting signals in a Distributed Antenna System is provided. The systemincludes a plurality of local Digital Access Units (DAUs) located at aLocal location. Each of the plurality of local DAUs is coupled to eachother and operable to route signals between the plurality of local DAUs.Each of the plurality of local DAUs includes one or more BaseTransceiver Station (BTS) RF connections, each of the plurality of BTSRF connections being operable to be coupled to one of one or moresectors of a BTS. The system also includes a plurality of remote DAUslocated at a Remote location. The plurality of remote DAUs are coupledto each other and operable to transport signals between the plurality ofremote DAUs.

According to another embodiment of the present invention, a system forrouting signals in a Distributed Antenna System is provided. The systemincludes a plurality of local Digital Access Units (DAUs) located at aLocal location. The plurality of local DAUs are coupled to each otherand operable to route signals between the plurality of local DAUs. Eachof the plurality of local DAUs have one or more RF input connectionsoperable to receive an RF signal from a sector of a Base TransceiverStation (BTS). The system also includes a plurality of remote DigitalAccess Units (DAUs) located at a Remote location. The plurality ofremote DAUs are coupled to the plurality of local DAUs and coupled toeach other. The system further includes a plurality of DRUs arranged incells. At least one of the plurality of DRUs is coupled to at least oneof the plurality of remote DAUs.

According to a specific embodiment of the present invention, a systemfor routing signals in a Distributed Antenna System is provided. Thesystem includes a first BTS having a plurality of sectors. Each of theplurality of sectors includes an RF port operable to receive an RFcable. The system also includes a second BTS having a plurality ofsectors. Each of the plurality of sectors includes an RF port operableto receive an RF cable. The system further includes a first local DAUlocated at a Local location. The first local DAU is connected to an RFport of a first sector of the first BTS through an RF cable and an RFport of a first sector of the second BTS through an RF cable. Moreover,the system includes a second local DAU located at a Local location. Thesecond local DAU is connected to an RF port of a second sector of thefirst BTS through an RF cable and an RF port of the second sector of thesecond BTS through an RF cable. The system also includes acommunications media connecting the first local DAU and the second localDAU, a mux/demux coupled to the first local DAU and the second localDAU, a network connection between the mux/demux and a second mux/demux,and a plurality of remote DAUs located at a Remote location andconnected to the second mux/demux. The plurality of remote DAUs arecoupled to each other and to a server.

According to another specific embodiment of the present invention, asystem for routing signals in a Distributed Antenna System is provided.The system includes an antenna operable to receive a signal from a BaseTransceiver Station (BTS), an off air repeater coupled to the antenna,and a local Digital Access Units (DAU) coupled to the off air repeater.The system also includes a first multiplexer/demultiplexer coupled tothe local DAU, a second multiplexer/demultiplexer coupled to the firstmultiplexer/demultiplexer, and a remote DAU coupled to the secondmultiplexer/demultiplexer. In an embodiment, the BTS is geographicallyseparated from the location of the local DAU.

According to an alternative embodiment of the present invention, asystem for routing signals in a Distributed Antenna System (DAS) isprovided. The system includes a plurality of Base Transceiver Stations(BTS), each having one or more sectors and a plurality of BTS RFconnections, each being coupled to one of the one or more sectors. Thesystem also includes a plurality of local Digital Access Units (DAUs)located at a Local location. Each of the plurality of local DAUs iscoupled to each other, operable to route signals between the pluralityof local DAUs, and coupled to at least one of the plurality of BTS RFconnections. The system further includes a plurality of remote DAUslocated at a Remote location. The plurality of remote DAUs are coupledto each other and operable to transport signals between the plurality ofremote DAUs.

According to another alternative embodiment of the present invention, asystem for routing signals in a DAS is provided. The system includes aplurality of local Digital Access Units (DAUs) located at a Locallocation. The plurality of local DAUs are coupled to each other andoperable to route signals between the plurality of local DAUs. Thesystem also includes a plurality of remote Digital Access Units (DAUs)located at a Remote location coupled to each other and operable totransport signals between the remote DAUs and each other and a pluralityof Base Transceiver Stations (BTS). The system further includes aplurality of Base Transceiver Station sector RF connections coupled tothe plurality of local DAUs and operable to route signals between theplurality of local DAUs and the plurality of Base Transceiver Stationssector RF connections and a plurality of DRUs connected to a pluralityof remote DAUs via at least one of a Ethernet cable, Optical Fiber, RFCable, Microwave Line of Sight Link, Wireless Link, or Satellite Link.

According to yet another alternative embodiment of the presentinvention, a system for routing signals in a DAS is provided. The systemincludes a first BTS having a plurality of sectors and a second BTShaving a plurality of sectors. Each of the plurality of sectors of thefirst BTS includes an RF port operable to receive an RF cable. Each ofthe plurality of sectors of the second BTS includes an RF port operableto receive an RF cable. The system also includes a first local DAUlocated at a Local location. The first local DAU is connected to an RFport of a first sector of the first BTS through an RF cable and an RFport of a first sector of the second BTS through an RF cable. The systemfurther includes a second local DAU located at a Local location. Thesecond local DAU is connected to an RF port of a second sector of thefirst BTS through an RF cable and an RF port of the second sector of thesecond BTS through an RF cable. Additionally, the system includes acommunications media connecting the first local DAU and the second localDAU, a mux/demux coupled to the first local DAU and the second localDAU, a network connection between the mux/demux and a second mux/demux,and a plurality of remote DAUs located at a Remote location andconnected to the second mux/demux. The plurality of remote DAUs arecoupled to each other and to a server.

Numerous benefits are achieved by way of the present invention overconventional techniques. For instance, embodiments of the presentinvention can virtually transport the hotel base stations to a remotelocation, which may be a considerable distance from the physicallocation (e.g., kilometers of separation). Additionally, embodimentsenable the routing capacity at the remote location. These and otherembodiments of the invention along with many of its advantages andfeatures are described in more detail in conjunction with the text belowand attached figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram according to one embodiment of the inventionshowing the basic structure and an example of the transport routingbased on having multiple 3 sector BTSs with 3 Digital Access Units(DAUs) at a Local Location, 3 DAUs at a Remote Location and RFinterfaces at the Remotes.

FIG. 2 is a block diagram according to one embodiment of the inventionshowing the basic structure and an example of the transport routingbased on having multiple 3 sector BTSs with 3 DAUs at a Local Location,3 DAUs at a Remote Location and Optical interfaces at the Remotes.

FIG. 3 is a block diagram according to one embodiment of the inventionshowing the basic structure and an example of the transport routingbased on having multiple 3 sector BTSs with 3 DAUs at a Local Location,3 Digital Remote Units (DRUs) at a Remote Location and Opticalinterfaces at the Remotes.

FIG. 4 is a block diagram illustrating a DAU, which contains physicalNodes and a Local Router, according to an embodiment of the presentinvention.

FIG. 5 is a block diagram illustrating a DRU according to an embodimentof the present invention.

FIG. 6 is a block diagram illustrating a DAS system according to anembodiment of the present invention.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

To accommodate variations in wireless subscriber loading at wirelessnetwork antenna locations at various times of day and for different daysof the week, there are several candidate conventional approaches.

One approach is to deploy many low-power high-capacity base stationsthroughout the facility. The quantity of base stations is determinedbased on the coverage of each base station and the total space to becovered. Each of these base stations is provisioned with enough radioresources, i.e., capacity and broadband data throughput to accommodatethe maximum subscriber loading which occurs during the course of theworkday and work week. Although this approach typically yields a highquality of service for wireless subscribers, the notable disadvantage ofthis approach is that many of the base stations' capacity is beingwasted for a large part of the time. Since a typical indoor wirelessnetwork deployment involves capital and operational costs which areassessed on a per-subscriber basis for each base station, the typicallyhigh total life cycle cost for a given enterprise facility is far fromoptimal.

A second candidate approach involves deployment of a DAS along with acentralized group of base stations dedicated to the DAS. A conventionalDAS deployment falls into one of two categories. The first type of DASis “fixed”, where the system configuration doesn't change based on timeof day or other information about usage. The remote units associatedwith the DAS are set up during the design process so that a particularblock of base station radio resources is thought to be enough to serveeach small group of DAS remote units. A notable disadvantage of thisapproach is that most enterprises seem to undergo frequentre-arrangements and re-organizations of various staff groups within theenterprise. Therefore, it's highly likely that the initial DAS setupwill need to be changed from time to time, requiring deployment ofadditional direct staff and contract resources with appropriate levelsof expertise regarding wireless networks.

The second type of DAS is equipped with a type of network switch whichallows the location and quantity of DAS remote units associated with anyparticular centralized base station to be changed manually. Althoughthis approach would appear to support dynamic DAS reconfiguration basedon the needs of the enterprise or based on time of day, it frequentlyimplies that additional staff resources would need to be assigned toprovide real-time management of the network. Another issue is that it'snot always correct or best to make the same DAS remote unitconfiguration changes back and forth on each day of the week at the sametimes of day. Frequently it is difficult or impractical for anenterprise IT manager to monitor the subscriber loading on each basestation. And it is almost certain that the enterprise IT manager has nopractical way to determine the loading at a given time of day for eachDAS remote unit; they can only guess the percentage loading.

Another major limitation of conventional DAS deployments is related totheir installation, commissioning and optimization process. Somechallenging issues which must be overcome include selecting remote unitantenna locations to ensure proper coverage while minimizing downlinkinterference from outdoor macro cell sites, minimizing uplinkinterference to outdoor macro cell sites, and ensuring properintra-system handovers while indoors and while moving from outdoors toindoors (and vice-versa). The process of performing such deploymentoptimization is frequently characterized as trial-and-error. Therefore,the results may not be consistent with a high quality of service.

According to embodiments of the present invention, a highly efficient,easily deployed and dynamically reconfigurable wireless network isprovided. The advanced system architecture provided by embodiments ofthe present invention provides a high degree of flexibility to manage,control, enhance and facilitate radio resource efficiency, usage andoverall performance of the distributed wireless network. This advancedsystem architecture enables specialized applications and enhancementsincluding, but not limited to, flexible simulcast, automatic trafficload-balancing, network and radio resource optimization, networkcalibration, autonomous/assisted commissioning, carrier pooling,automatic frequency selection, radio frequency carrier placement,traffic monitoring, and/or traffic tagging. Embodiments of the presentinvention can also serve multiple operators, multi-mode radios(modulation-independent) and multiple frequency bands per operator toincrease the efficiency and traffic capacity of the operators' wirelessnetworks.

Accordingly, embodiments of the DAS network provide a capability forFlexible Simulcast. With Flexible Simulcast, the amount of radioresources (such as RF carriers, LTE Resource Blocks, CDMA codes or TDMAtime slots) assigned to a particular DRU or group of DRUs can be set viasoftware control to meet desired capacity and throughput objectives orwireless subscriber needs. Applications of the present invention aresuitable to be employed with distributed base stations, distributedantenna systems, distributed repeaters, mobile equipment and wirelessterminals, portable wireless devices, and other wireless communicationsystems such as microwave and satellite communications.

A distributed antenna system (DAS) provides an efficient means ofutilization of base station resources. The base station or base stationsassociated with a DAS can be located in a central location and/orfacility commonly known as a base station hotel. The DAS networkcomprises one or more digital access units (DAUs) that function as theinterface between the base stations and the digital remote units (DRUs).The DAUs can be collocated with the base stations. The DRUs can be daisychained together and/or placed in a star configuration and providecoverage for a given geographical area. The DRUs are typically connectedwith the DAUs by employing a high-speed optical fiber link. Thisapproach facilitates transport of the RF signals from the base stationsto a remote location or area served by the DRUs. A typical base stationcomprises 3 independent radio resources, commonly known as sectors.These 3 sectors are typically used to cover 3 separate geographicalareas without creating co-channel interference between users in the 3distinct sectors. In other embodiments, additional sectors areassociated with each BTS, for example, up to or more than 12 sectors.

An embodiment shown in FIG. 1 illustrates a DAS network architectureaccording to an embodiment of the present invention and provides anexample of a data transport scenario between multiple 3 sector BaseStations and multiple remotely located DAUs. BTSs 1 through N areconnected to DAU1, DAU2, and DAU3 (i.e., local DAUs) by an RF cable inthe illustrated embodiment. Each of the local DAUs are connected toserver 130. A Coarse Wavelength Division Multiplexer/Demux (CWDM) isutilized to facilitate data transport over a single optical fiber 112from the local location to the remote location. Another embodiment ofthe data transport system could use a Dense Wavelength DivisionMultiplexer (DWDM). In the illustrated embodiment, the DAUs at the Locallocation are coupled together using cables 140 and 141 to achieverouting of the RF signals. The DAUs at the Remote Location are coupledtogether using cables 142 and 143. In some embodiments, three sectorBTSs are connected to a daisy chained group of DAUs at both the localand remote locations.

It should be noted that although FIG. 1 illustrates one or more BTSs 1through N, the BTSs are not required by the present invention and someembodiments only include elements illustrated to the right of the HotelPlane. As will be evident to one of skill in the art, the systemsdescribed herein can be operable to connect to BTSs that are provided bydifferent entities, such as telecommunications operators. Thus, someembodiments utilize a DAU that has one or more BTS RF connections. Eachof the one or more BTS RF connections is operable to be coupled to oneof one or more sectors of a BTS. As described herein the connectionbetween the BTS and the DAU can be made using an RF cable, or acombination of wireless and optical/RF cables depending on theparticular implementation.

FIG. 1 depicts a DAS system employing multiple Digital Access Units(DAUs) at the Local location and multiple Digital Access Units (DAUs) atthe Remote location. In accordance with the present invention, each DAUprovides unique information associated with each DAU, which uniquelyidentifies data received and transmitted by a particular DAU. Asillustrated in FIG. 1, the 3 sector base stations are connected to adaisy chained DAS network, although other configurations are includedwithin the scope of the present invention.

One feature of embodiments of the present invention is the ability toroute Base Station radio resources among the DAUs or group(s) of DAUs.In order to route radio resources available from one or more BaseStations, it is desirable to configure the individual router tables ofthe DAUs in the DAS network. This functionality is provided byembodiments of the present invention.

The DAUs are networked together to facilitate the routing of signalsamong multiple DAUs. The DAUs support the transport of the RF downlinkand RF uplink signals between the Base Station and the various DAUs.This architecture enables the various Base Station signals to betransported simultaneously to and from multiple DAUs. PEER ports areused for interconnecting DAUs.

The DAUs have the capability to control the gain (in small incrementsover a wide range) of the downlink and uplink signals that aretransported between the DAU and the base station (or base stations)connected to that DAU. This capability provides flexibility tosimultaneously control the uplink and downlink connectivity of the pathbetween a particular Remote DAU (or a group of DAUs) and a particularbase station sector.

A single optical fiber can be used for the transportation of databetween the Local DAUs and the Remote DAUs by using a Coarse WavelengthDivision Multiplexer (CWDM) and De-multiplexer, connected, for example,through optical cable 112. Embodiments of the present invention are notlimited to the use of an optical cable 112 and other communicationsmedia can be employed including Ethernet cable, Microwave Line of SightLink, Wireless Link, Satellite Link, or the like.

Referring to FIG. 1, optical fiber 112 connects the local CWDM Mux/Demuxto the Remote CWDM Mux/Demux. In the illustrated embodiment, threeoutputs are provided by the Remote CWDM Mux/Demux, for example, threedifferent optical wavelengths. The optical cables 113 connect the RemoteCWDM Mux/Demux to the remote DAUs (DAU 4, DAU 5, and DAU 6). Thus,embodiments of the present invention provide for Local DAUs (that can beconnected to each other in the illustrated daisy chain or otherconfiguration) that are connected to Remote DAUs, which can also beconnecting to each other in a daisy chain or other configuration. Asshown in FIG. 1, cables 140/141 and 142/143, which connect the Local andRemote DAUs, respectively, can be Ethernet cable, Optical cable,Microwave Line of Sight Link, Wireless Link, Satellite Link, or thelike. Additionally, although the connections between the BTSs and thelocal DAUs are illustrated as RF cables, this is not required byembodiments of the present invention and other communications media canbe utilized. Moreover, although the remote DAUs include an optical cableconnection to the remote CWDM Mux/Demux and an RF cable in the RemotePlane, the connections in the Remote plane (e.g., to mobile accessequipment) can be made using other communications media.

As illustrated in FIG. 1 at the Remote location, RF outputs are providedby the DAUs in the remote plane. In the illustrated embodiment, the DAUsare interconnected at the remote location (e.g., the DAUs are daisychained at the remote location). Thus, in the embodiment illustrated inFIG. 1, the RF signals present in the Hotel Plane are replicated in theRemote Plane. In other words, embodiments of the present inventionvirtualize the Hotel Plane at the Remote Plane. As an example, thesignals carried by the RF cable connecting Sector 1 (120) and DAU 1(102) are available in the RF cable connected to DAU 4 (105). As aresult, signals from BTS 1 through BTS N are virtually extended from theHotel Plane to the Remote Plane, which may be physically separated bykilometers of distance, overcoming transmission loss and other adverseeffects that would be produced if the RF cables connected to the BTSswere used in an attempt to bridge the distance between the Hotel Planeand the Remote Plane. The virtual extension of the Hotel Plane to theRemote Plane enables the RF cables in the Remote Plane to be connectedto appropriate equipment, providing the BTSs virtually in the RemotePlane.

Embodiments of the present invention provide methods and systems thatenable capacity shifting. As an example, a signal can be routed fromBTS1, sector 1 (121), through an RF cable to DAU1 (102), transportedover the optical fiber 111 through the Local CWDM Mux/Demux, overoptical cable 112 to the Remote CWDM Mux/Demux, through optical cable113 to DAU4 (105), and then routed down to DAU5 (106) via cable 142 andthen output through the RF cable connected to DAU5. Thus, usingembodiments of the present invention, it is possible to control thetransmission of the signal at the remote location from any of the BTSsectors (e.g., BTS1, sector 1). As illustrated, embodiments of thepresent invention provide the flexibility to route signals from apredetermined RF input cable connected to the Local DAUs to apredetermined RF output cable connected to the Remote DAUs.Additionally, in the reverse direction, signals can be routed from apredetermined RF input cable connected to the Remote DAUs to apredetermined RF output cable connected to the Local DAUs. As anexample, a signal could be received on the RF cable connected to DAU5(106), routed to DAU4 (105), and then through the network. Thus,embodiments of the present invention provide the flexibility at theremote location to move capacity from one device to another, forexample, if the remote DAUs are not physically in the same location,(e.g., DAU4 (105) is in one building, DAU5 (106) is located in anotherbuilding, and DAU6 (107) is located in yet another building). In thatcase, flexibility is provided to be able to route signals in bothdirections onto different optical cables.

Referring to FIG. 1, embodiments of the present invention provide for avirtual extension or replication of the RF cables in the Hotel Plane tothe RF cables in the Remote Plane. Thus, the BTSs have been virtuallytransported from the base station hotel to the remote location since theoutput of the RF cables in the Remote Plane can be identical to theinputs to the RF cables in the Hotel Plane, enabling interface withmobile access equipment. Although the connections in the Hotel Plane areillustrated as RF cables, this is not required by embodiments of thepresent invention and other communications media are included within thescope of the present invention, including Ethernet cable, Optical Fiber,Microwave Line of Sight Link, Wireless Link, or Satellite Link. In someembodiments, summing is utilized to provide a system in which a singleDAU port is connected to a plurality of BTSs. For example, BTS 1, sector1 (120), and BTS N, sector 1 (121) could be summed and then connected toa single port in DAU 1 (102).

According to embodiments of the present invention, DAUs are utilized atboth the Local and Remote locations. The DAU communicates with a NetworkOperational Control (NOC). The NOC sends commands and receivesinformation from the DAS network. The DAS network can include aplurality of DAUs and DRUs. The DAU communicates with the network ofDRUs and the DAU sends commands and receives information from the DRUs.The DAUs include physical nodes that accept and deliver RF signals andoptical nodes that transport data. A DAU can include an internal serveror an external server. The server is used to archive information in adatabase, store the DAS network configuration information, and performvarious traffic related processing. The server can be used tocommunicate information from the DAS Network to the NOC.

Additionally, the DRU communicates with the DAU. In some embodiments,the DRU does not communicate with the NOC. The DRU receives commandsfrom the DAU and delivers information to the DAU. The DRUs includephysical nodes that accept and deliver RF signals and optical nodes thattransport data. As illustrated in FIG. 1, the use and connection of theDAUs to each other in the Remote location provide benefits not availablein systems in which DRUs are utilized in the Remote location, forexample, the use of server 131 in connection with the remote DAUs, sincein some implementations, a server is not used with remote DRUs. In otherimplementations, the remote DRUs can be coupling to each other and canbe connected to a server as discussed in relation to FIG. 3. As shown inFIG. 1, the remote DAUs are connected through cables 142 and 143.

FIG. 6 is a block diagram illustrating a DAS system architectureaccording to an embodiment of the present invention. In this system, oneor more of the connections between the BTS sectors and the DAU inputsutilize a wireless connection for at least a portion of thecommunication path. As illustrated in FIG. 6, one or more off airrepeaters (Repeater 1 (142), Repeater 2 (143), and Repeater 3 (144))receives an RF signal (e.g., an analog RF signal) from an antenna(antennas 610, 611, and 612). The off air repeater (which can bereferred to simply as a repeater) receives the RF signal from theantenna and converts the RF signal into an optical signal that can betransported over an optical cable to a DAU (e.g., DAU 1 (102), DAU 2(103), and DAU 3 (104). A BTS (not shown) located at a location that isgeographically separated from the other system elements is coupled to anantenna (not shown) that transmits the wireless signals that arereceived by antennas 610, 611, or 612. Thereby, the sectors of thegeographically separated BTS are in wireless communication with the offair repeaters through the corresponding set of antennas. Accordingly,this architecture enables an additional Hotel Plane located between theantennas 610, 611, and 612 and the off air repeaters 142, 143, and 144,effectively extending the original Hotel Plane defined by the RFconnections from BTS 1 to the DAUs. As illustrated, a wirelessconnection is established between the sectors of the geographicallyseparated BTS (now shown) and the off-air repeater. Using the off airrepeaters, an optical connection is thereby established to the DAUs.

As an example, the geographically separated BTS (not shown) could belocated at a given distance, for example, 2 km from the facilitiescontaining the off air repeaters 142-144, which receive the wireless RFsignals at their respective antennas from one of the sectors of theremote BTS, and the DAUs. These embodiments provide connectivity to ageographically separated BTS in conditions in which physicallyco-locating this BTS with the other equipment illustrated in FIG. 6, forexample, the DAUs 1-3, is not convenient or expeditious.

Thus, the definition of Hotel Plane is not limited to the RF connectionsto the BTSs as discussed in relation to FIG. 1 and illustrated in FIG.6, but also includes RF connections to one or more antennas that receivesignals from a geographically separated BTS. It should be noted that thelocal DAU can include both one or more RF connections operable toreceive an RF signal from a co-located BTS and one or more opticalconnections operable to receive an optical signal from an off airrepeater, which can be in communication with a geographically separatedBTS. One of ordinary skill in the art would recognize many variations,modifications, and alternatives.

As illustrated in FIG. 6, an optical fiber is used to connect Repeaters1-3 (142, 143, and 144) to the DAUs 1-3 (102, 103, and 104). Therefore,the DAUs provide inputs for both RF cables, suitable for connections toBTSs, as well as optical cables, suitable for connections to off-airrepeaters, which receive signals from remote BTSs.

FIG. 2 is a block diagram according to one embodiment of the inventionshowing the basic structure and an example of the transport routingbased on having multiple 3 sector BTSs with 3 DAUs at a Local Location,3 DAUs at a Remote Location and Optical interfaces at the Remotes. Asillustrated in FIG. 2, communication between the plurality of remoteDAUs (i.e., DAU 4 (202), DAU 5 (203), and DAU 6 (204)) and thecorresponding cells of DRUs (i.e., Cell 1, Cell 2, and Cell 3) isprovided via optical cables 211, 212, and 213, respectively. Thus, thisarchitecture provides communication to the mobile devices through theDRUs.

As shown in FIG. 2, the individual base station sector's radio resourcesare transported to a daisy-chained network of DRUs. Each individualsector's radio resources provide coverage to an independent geographicalarea via the networked DRUs. FIG. 2 demonstrates how three cells, eachcell comprising an independent network of 7 DRUs, provide coverage to agiven geographical area. A server is utilized to control the switchingfunction provided in the DAS network. Referring to FIG. 2 and by way ofexample, DAU 1 (205) receives downlink signals and transmits uplinksignals from and to BTS Sector 1 (120). DAU 1 translates the RF signalsto optical signals for the downlink and translates the optical signalsto RF signals for the uplink. The optical fiber cable (215) transportsthe desired signals to and from CWDM (221) whereby the distinct DAUoptical wavelengths are multiplexed and de-multiplexed. Optical cable(214) transports all the optical signals between CWDM (221) and CWDM(220). DAU 4 (202) transports the optical signal to and from CWDM (220).DAU 4 (202) transports the uplink and downlink data to and from a daisychain of DRUs. The other DRUs in the daisy chain are involved in passingthe optical signals onward to DRU 1 (247). Although not illustrated inFIG. 2, it will be appreciated that RF cables 270 connect to the BTSs.

FIG. 3 depicts a DAS system employing multiple Digital Access Units(DAUs) at the Local location and multiple Digital Remote Units (DRUs) atthe Remote location. In accordance with the present invention, each DRUprovides unique information associated with each DRU, which uniquelyidentifies data received and transmitted by a particular Digital RemoteUnit.

DRU 24 (302) is located at the Remote location, and is connected viadaisy-chain to 7 additional DRU units that occupy Cell 1 (350).Similarly, DRU 25 (303) connects to a daisy chain of DRUs occupying Cell3 and DRU 26 (304) connects to a daisy-chain of DRUs occupying Cell 2.The remote DRUs 24, 25 and 26 are interconnected which facilitates therouting of signals between DRUs. The embodiment illustrated in FIG. 3provides a daisy chain architecture, which can be compared with the stararchitecture that can be implemented using the embodiment illustrated inFIG. 2, for example, by providing multiple optical outputs from theremote DAUs. As an example, in addition to optical cable 211, anadditional optical cable (not shown) could be provided at the output ofDAU 2 (202). One of ordinary skill in the art would recognize manyvariations, modifications, and alternatives.

The servers illustrated herein, for example, server 330 provide uniquefunctionality in the systems described herein. The following discussionrelated to server 330 may also be applicable to other servers discussedherein an illustrated in the figures. Server 330 can be used to set upthe switching matrices to allow the routing of signals between theremote DRUs. The server 330 can also store configuration information,for example, if the system gets powered down or one DRU goes off-lineand then you power up the system, it will typically need to bereconfigured. The server 330 can store the information used inreconfiguring the system and/or the DRUs.

FIG. 4 shows the two elements in a DAU, the Physical Nodes (400) and theLocal Router (401). The Physical Nodes translate the RF signals tobaseband for the Downlink and from baseband to RF for the Uplink. TheLocal Router directs the traffic between the various LAN Ports, PEERPorts and the External Ports. The physical nodes connect to the BTS atradio frequencies (RF). The physical nodes can be used for differentoperators, different frequency bands, different channels, or the like.The physical nodes can combine the downlink and uplink signals via aduplexer or they can keep them separate, as would be the case for asimplex configuration.

FIG. 4 shows an embodiment whereby the physical nodes have separateoutputs for the uplinks (405) and separate inputs for the downlink paths(404). The physical node translates the signals from RF to baseband forthe downlink path and from baseband to RF for the uplink path. Thephysical nodes are connected to a Local Router via external ports(409,410)). The router directs the uplink data stream from the LAN andPEER ports to the selected External U ports. Similarly, the routerdirects the downlink data stream from the External D ports to theselected LAN and PEER ports.

In one embodiment, the LAN and PEER ports are connected via an opticalfiber to a network of DAUs and DRUs. The network connection can also usecopper interconnections such as CAT 5 or 6 cabling, or other suitableinterconnection equipment. The DAU is also connected to the internetnetwork using IP (406). An Ethernet connection (408) is also used tocommunicate between the Host Unit and the DAU. The DRU can also connectdirectly to the Remote Operational Control center (407) via the Ethernetport.

FIG. 5 shows the two elements in a DRU, the Physical Nodes (501) and theRemote Router (500). The DRU includes both a Remote Router and PhysicalNodes. The Remote Router directs the traffic between the LAN ports,External Ports and PEER Ports. The physical nodes connect to the BTS atradio frequencies (RF). The physical nodes can be used for differentoperators, different frequency bands, different channels, etc. FIG. 5shows an embodiment whereby the physical nodes have separate inputs forthe uplinks (504) and separate outputs for the downlink paths (503). Thephysical node translates the signals from RF to baseband for the uplinkpath and from baseband to RF for the downlink path. The physical nodesare connected to a Remote Router via external ports (506,507). Therouter directs the downlink data stream from the LAN and PEER ports tothe selected External D ports. Similarly, the router directs the uplinkdata stream from the External U ports to the selected LAN and PEERports. The DRU also contains a Ethernet Switch (505) so that a remotecomputer or wireless access points can connect to the internet.

In some embodiments, the DAU is connected to a host unit/server, whereasthe DRU does not connect to a host unit/server. In these embodiments,parameter changes for the DRU are received from a DAU, with the centralunit that updates and reconfigures the DRU being part of the DAU, whichcan be connected to the host unit/server. Embodiments of the presentinvention are not limited to these embodiments, which are described onlyfor explanatory purposes.

It is also understood that the examples and embodiments described hereinare for illustrative purposes only and that various modifications orchanges in light thereof will be suggested to persons skilled in the artand are to be included within the spirit and purview of this applicationand scope of the appended claims.

Table 1 is a glossary of terms used herein, including acronyms.

Table 1 Glossary of Terms ACLR Adjacent Channel Leakage Ratio ACPRAdjacent Channel Power Ratio ADC Analog to Digital Converter AQDM AnalogQuadrature Demodulator AQM Analog Quadrature Modulator AQDMC AnalogQuadrature Demodulator Corrector AQMC Analog Quadrature ModulatorCorrector BPF Bandpass Filter CDMA Code Division Multiple Access CFRCrest Factor Reduction DAC Digital to Analog Converter DET DetectorDHMPA Digital Hybrid Mode Power Amplifier DDC Digital Down Converter DNCDown Converter DPA Doherty Power Amplifier DQDM Digital QuadratureDemodulator DQM Digital Quadrature Modulator DSP Digital SignalProcessing DUC Digital Up Converter EER Envelope Elimination andRestoration EF Envelope Following ET Envelope Tracking EVM Error VectorMagnitude FFLPA Feedforward Linear Power Amplifier FIR Finite ImpulseResponse FPGA Field-Programmable Gate Array

GSM Global System for Mobile communications

I-Q In-phase/Quadrature IF Intermediate Frequency

LINC Linear Amplification using Nonlinear Components

LO Local Oscillator LPF Low Pass Filter MCPA Multi-Carrier PowerAmplifier MDS Multi-Directional Search OFDM Orthogonal FrequencyDivision Multiplexing PA Power Amplifier PAPR Peak-to-Average PowerRatio PD Digital Baseband Predistortion PLL Phase Locked Loop QAMQuadrature Amplitude Modulation QPSK Quadrature Phase Shift Keying RFRadio Frequency RRH Remote Radio Head RRU Remote Radio Head Unit SAWSurface Acoustic Wave Filter UMTS Universal Mobile TelecommunicationsSystem UPC Up Converter WCDMA Wideband Code Division Multiple Access

WLAN Wireless Local Area Network

1. (canceled)
 2. A system for routing signals in a Distributed AntennaSystem, the system comprising: a plurality of local Digital Access Units(DAUs) located at a local location, each of the plurality of local DAUsbeing coupled to each other and operable to route signals between theplurality of local DAUs, wherein each of the plurality of local DAUsincludes one or more Base Transceiver Station (BTS) radiofrequencyconnections, each of the plurality of BTS radiofrequency connectionsbeing operable to be coupled to one of one or more sectors of a BTS; anda plurality of remote DAUs located at a remote location, wherein theplurality of remote DAUs are coupled to each other and operable totransport signals between the plurality of remote DAUs, and wherein theplurality remote DAUs are connected to the plurality local DAUs.
 3. Thesystem of claim 3, further comprising: a local multiplexer/demultiplexercoupled to the plurality of local DAUs; and a remotemultiplexer/demultiplexer coupled to the plurality of remote DAUs;wherein the local multiplexer/demultiplexer and the remotemultiplexer/demultiplexer are communicatively coupled.
 4. The system ofclaim 3, wherein the multiplexer/demultiplexer and the remotemultiplexer/demultiplexer are Coarse Wavelength DivisionMultiplexer/Demux (CWDM) or a Dense Wavelength Division Multiplexer(DWDM) systems.
 5. The system of claim 2, wherein the plurality of localDAUs are connected to the plurality of remote DAUs via at least one CWDMmultiplexer/demultiplexer and at least one optical fiber.
 6. The systemof claim 2, wherein the plurality of local DAUs are connected to theplurality of remote DAUs via at least one DWDM multiplexer/demultiplexerand at least one optical fiber.
 7. The system of claim 2, furthercomprising a server coupled to each of the plurality of remote DAUs. 8.The system of claim 2, wherein a single DAU port is operable to beconnected to a plurality of BTSs.
 9. A system for routing signals in aDistributed Antenna System, comprising: a first remote digital accessunit (DAU), wherein the first remote DAU is one of a plurality of remoteDAUs, wherein the plurality of remote DAUs are communicatively coupledto each other, and wherein the first remote DAU is configured to receivesignals from a first base transceiver station (BTS); a first cell,wherein the first cell includes a first plurality of digital remoteunits (DRUs), wherein the first plurality of DRUs are communicativelycoupled to each other; wherein the first DAU is configured to routesignals to the first cell, and wherein one or more DRUs of the firstplurality of DRUs are configured to transmit the routed signals.
 10. Thesystem of claim 9, further comprising: a first local DAU, wherein thefirst local DAU is one of a plurality of local DAUs, wherein theplurality of local DAUs are communicatively coupled to each other, andwherein the first local DAU is configured to receive signals from thefirst BTS; and wherein the first local DAU is configured to routesignals from the first BTS to the first remote DAU.
 11. The system ofclaim 10, further comprising: a local multiplexer/demultiplexer, whereinthe local multiplexer/demultiplexer is configured to communicate witheach of the plurality of local DAUs; a remote multiplexer/demultiplexer,wherein the remote multiplexer/demultiplexer is configured tocommunicate with each of the plurality of remote DAUs; wherein the firstlocal DAU is configured to route signals to the localmultiplexer/demultiplexer; wherein the local multiplexer/demultiplexeris configured to route signals to the remote multiplexer/demultiplexer;and wherein the remote multiplexer/demultiplexer is configured to routesignals to the first remote DAU.
 12. The system of claim 10, wherein thefirst local DAU is further configured to receive signals for a secondBTS.
 13. The system of claim 9, wherein the first remote DAU is furtherconfigured to receive signals from a second BTS.
 14. The system of claim13, wherein the first remote DAU is further configured to route signalsfrom the second BTS to a second cell, wherein the second cell includes asecond plurality of digital remote units (DRUs), wherein the secondplurality of DRUs are communicatively coupled to each other; and whereinone or more DRUs of the second plurality of DRUs are configured totransmit the signals.
 15. The system of claim 9, wherein routing iscontrolled by a server.
 16. A method for routing signals in aDistributed Antenna System, comprising: receiving, by a first remotedigital access unit (DAU), signals from a first base transceiver station(BTS), wherein the first remote DAU is one of a plurality of remoteDAUs, and wherein the plurality of remote DAUs are communicativelycoupled to each other; routing, by the first remote DAU, signals to afirst cell, wherein the first cell includes a first plurality of digitalremote units (DRUs), wherein the first plurality of DRUs arecommunicatively coupled to each other; and transmitting, by one or moreDRUs of the first plurality of DRUs, the routed signals.
 17. The methodof claim 16, further comprising: receiving, by a first local DigitalAccess Unit (DAU), signals from the first BTS, wherein the first localDAU is one of a plurality local DAUs, and wherein the plurality of localDAUs are communicatively coupled to each other; routing, by the firstlocal DAU, signals to the first remote DAU.
 18. The method of claim 17,wherein routing signals to the first remote DAU includes: routing, bythe first local DAU, signals to a local multiplexer/demultiplexer,wherein the local multiplexer/demultiplexer is configured to communicatewith each of the plurality of local DAUs; routing, by the localmultiplexer/demultiplexer, signals to a remotemultiplexer/demultiplexer, wherein the remote multiplexer/demultiplexeris configured to communicate with a plurality of remote DAUs; routing,by the remote multiplexer/demultiplexer, signals to the first remoteDAU.
 19. The method of claim 17, further comprising: receiving, by thefirst local DAU, signals from a second BTS.
 20. The method of claim 16,further comprising: receiving, by the first remote DAU, signals from asecond BTS.
 21. The method of claim 20, further comprising: routing, bythe first remote DAU, signals from the second BTS to a second cell,wherein the second cell includes a second plurality of digital remoteunits (DRUs), wherein the second plurality of DRUs are communicativelycoupled to each other; and transmitting, by one or more DRUs of thesecond plurality of DRUs, the signals.